1. Field of the Invention
The present invention relates to a memory management device, an image forming apparatus, and an image forming method, and particularly relates to memory usage in a virtual memory system.
2. Description of the Related Art
Usually, under a virtual memory mapping scheme, physical memory handling is controlled by a mapping mechanism managed by an operating system (hereinafter referred to as an OS). Therefore, it is difficult for the user to handle the physical memory freely. Consequently, interprocess cooperation is not achieved so that the amount of memory that can be handled is limited.
When memory space is managed by the OS, repetitively using and freeing memory results in the memory being finely consumed so that fragmentation occurs in the memory region.
For example, in a device handling large-capacity image data, such as an image forming apparatus, it is difficult to define a sufficient memory region due to the occurrence of fragmentation. Therefore, successive large-capacity memories are defined with difficulty.
Consequently, the above-described configuration results in data being processed with low speed.
To address these difficulties, the following exemplary known technology presents a virtual memory system that can avoid low-speed data processing without consuming unnecessary physical memory for a page table.
Under such a system, an address conversion table generator is connected to a system bus and accessed by a central processing unit (CPU) when a translation look-aside buffer (TLB) mistake is made. Then, each time the CPU accesses the address conversion table generator, an appropriate page table entry is generated under a previously made rule.
Thus, the region of the memory may not be used by accessing the address conversion table generator. Further, the CPU can set the rule under which the address conversion table generator generates a page table.
However, the above-described method is a technology for reducing the consumption of the memory of the page table, and the amount of a memory region defined through the above-described method is significantly small.
Therefore, the above-described method is insufficient to define successive large capacity memory spaces used for image data handled by an image forming apparatus.
Further to the above-described known technology, an additional attempt to avoid low-speed data processing involves a memory-region management method for ensuring a virtual memory region managed by an OS and an image memory region provided to store image data managed by anything but the OS on a rewritable memory.
The above-described known technology allows for performing memory management appropriate for the architecture of the OS, and increasing the processing efficiency and the memory use efficiency.
However, even though the above-described memory region management can improve the processing speed, it is difficult to map the memory region managed by anything but the OS to virtual memory.
The present invention addresses shortcomings of known technologies to increase the efficiency with which a virtual memory system handles successive data items.